The present invention relates to melting of metals, metal alloys or any conductive material by electric arcs.
In metallurgy, arc furnaces are used which permit the circulation of an electric current through a conductive mass to be melted by means of an electric arc created between such a mass and an electrode disposed above.
Actually, furnaces of this type are usually operated by a three-phase alternating electric current applied to three electrodes extending through the arched roof of the furnace towards the mass to be melted. Thus, three arcs are created, respectively between each of the electrodes and the mass to be melted, which represents the neutral, and each of the arcs functions with alternating current, each electrode being alternately a positive and a negative pole. This usual procedure has the disadvantages of being expensive due to rapid consumption of the electrodes, as well as due to limitations of the magnitude of the electric heating due to difficulties connected with the instability of the arcs.
In order to resolve these problems, a solution has already been proposed according to which the electric power is produced by direct current with the creation of a single arc. This known arrangement requires, however, another electrode of opposite polarity from that which is disposed above the mass to be melted and extending through the bottom of the furnace to assure by electrical contact with the bottom of this mass a return flow of the current. An electrode extending through the bottom of the furnace creates, however, some difficulties connected with the mounting and function of such an electrode. The technological limits due to the necessity to pass this electrode through the refractory wall of the furnace, the contact of this electrode with the metal during the melting, the dimension of the electrode, the necessity of cooling the same, etc., make it very difficult to apply through such electrodes heavy electric currents which are desirable for furnaces of great capacity.